His major points (he has several more, but I'll put up some of the more compelling ones):
1) Autism is increasing, as is vitamin D deficiency, and the autism epidemic came upon us at the same time the major health authorities advised us to eschew the sun.
2) Vitamin D is likely central to brain development as a key helper in neural development and neuroprotection. In addition, autism is likely mediated by inflammation, and vitamin D is a key player in anti-inflammatory processes. Also, vitamin D enables glutathione, the "master antioxidant," clear our system of free radicals, and glutathione also acts as a chelating agent to bind toxic heavy metals such as mercury, which kids with autism have a tough time clearing from their systems.
3) Williams syndrome, a chromosomal disease (among other things) results in abnormally high levels of circulating active vitamin D in early childhood, results in kids who are especially social and overfriendly - rather the opposite of autism symptoms.
4) During pregnancy, boys' brains are bathed in testosterone, and girls' brains in estrogen. Estrogen is known to have many vitamin D enhancing properties. This could account for the 4:1 ratio of boys to girls suffering from autism.
5) Studies show autism births occur most often in March, at the end of winter, when vitamin D levels would be lowest.
6) African Americans seem to suffer from a higher rate of autism, and they also have a higher rate of vitamin D deficiency than people with lighter skin. In Europe, the children of darker-skinned immigrants have higher rates of autism also.
7) Rickets, due to vitamin D deficiency, is characterized by hypotonia (poor muscle tone) and developmental delay, as is autism.
8) Autism seems to be higher among the kids of highly educated women, and they are more likely to follow guidelines for sun restriction for themselves and their children.